The present invention relates to an X-ray computed tomography (CT) scanner having an optical transmission system responsible for optical transmission between a rotator and a stator that are arranged to be opposed to each other in a non-contact state in a gantry, both the rotator and stator being arranged therein to perform rotating X-ray beam radiation on a patient inserted into an opening of the gantry.
In recent years, an optical cable has preferably been employed for signal transmission using light signals between a plurality of separated components. When such a plurality of components include moved components, it is very difficult to connect the optical cable to the moved components, thereby the optical cable not being able to be used readily to transmit light signals. Specifically, if the moved components make a rotational motion continuously or repeatedly for a certain period of time, the optical cable would become entangled.
As one of known methods of effecting optical transmission between a moving component and a stationary component that are opposed to each other in a non-contact state, there is an optical system including lenses, reflectors, and others.
For instance, a conventional medical-purpose X-ray CT scanner frequently employs such an optical system. The X-ray CT scanner has a gantry incorporating a stator and a rotator. The rotator, which is formed into a ring shape having an outer circumferential surface, is equipped with an X-ray tube and an X-ray detector at given positions for X-ray diagnosis. On one hand, the stator is made of part of stationary components, for instance, and arranged outside the rotator in its radial direction with an appropriate space left between both of the rotator and stator.
Under such arrangement, the foregoing optical system comprises a plurality of light emitting elements mounted on the outer circumferential surface of the rotator, a light receiving element mounted on the stator, and a plurality of reflectors and lenses arranged in the space between the rotator and stator.
Each of the light emitting elements radially radiates information such as a control signal and an image signal concerning an X-ray scan in the form of a light beam. The radially radiated light beam is to reach the light receiving element with passing complicatedly through the lenses, reflectors, and the like. A light beam has directivity. One light beam, which is propagated by one of the plurality of light emitting elements that has rotated to approach the position opposed at least to the stator, is therefore received readily, but the other light beam propagated by the other light emitting elements located at the other positions is hardly received. The plurality of reflectors, lenses, and the like are therefore arranged between the rotator and stator in order to expand a zone sensitive to incoming light.
In the foregoing prior art that uses the optical system transmitting a light beam in the radial direction, when an attempt is made to improve convergency, it becomes necessary to use high-performance lenses and numerous reflectors in combination. Eventually, the optical transmission system for an X-ray CT scanner becomes very complex and expensive.